PES Skill Sheets.book - Capital High School

Name: Date:
17.1 Magnetic Earth
Earth’s magnetic field is very weak compared with the strength of the field on the surface of the ceramic magnets
you probably have in your classroom. The gauss is a unit used to measure the strength of a magnetic field. A
small ceramic permanent magnet has a field of a few hundred up to 1,000 gauss at its surface. At Earth’s surface,
the magnetic field averages about 0.5 gauss. Of course, the field is much stronger nearer to the core of the planet.
1. What is the source of Earth’s magnetic field according to what you have read in chapter 17?
2. Today, Earth’s magnetic field is losing approximately 7 percent of its strength every 100 years. If the
strength of Earth’s magnetic field at its surface is 0.5 gauss today, what will it be 100 years from now?
3. Describe what you think might happen if Earth’s magnetic field continues to lose strength.
4. The graphic to the right illustrates one piece of evidence that proves the
reversal of Earth’s poles during the past millions of years. The ‘crust’ of
Earth is a layer of rock that covers Earth’s surface. There are two kinds of
crust—continental and oceanic. Oceanic crust is made continually (but
slowly) as magma from Earth’s interior erupts at the surface. Newly formed
crust is near the site of eruption and older crust is at a distance from the site.
Based on what you know about magnetism, why might oceanic crust rock
be a record of the reversal of Earth’s magnetic field? (HINT: What happens
to materials when they are exposed to a magnetic field?)
5. The terms magnetic south pole and geographic north pole refer to locations
on Earth. If you think of Earth as a giant bar magnet, the magnetic south
pole is the point on Earth’s surface above the south end of the magnet. The
geographic north pole is the point where Earth’s axis of rotation intersects
its surface in the northern hemisphere. Explain these terms by answering the
following questions.
a. Are the locations of the magnetic south pole and the geographic north
pole near Antarctica or the Arctic?
b. How far is the magnetic south pole from the geographic north pole?
c. In your own words, define the difference between the magnetic south pole and the geographic north
pole.
6. A compass is a magnet and Earth is a magnet. How does the magnetism of a compass work with the
magnetism of Earth so that a compass is a useful tool for navigating?
17.1